A novel class of proteins that regulate G protein signaling (RGS) have recently been discovered. Thus far this family of RGS proteins, containing at least 20 members, have been identified on the basis of i) a 120 amino acid RGS domain , ii) their ability to bind specifically to Galpha proteins and iii) their ability to potentiate the intrinsic GTPase activity of the Galpha protein and thus expedite the termination of its activity. It remains unknown whether RGS proteins are themselves regulated, perhaps by protein phosphorylation. Therefore, the purpose of the proposed research is to investigate the biochemical pathways which may regulate the activities of RGS proteins (RGS10 in particular) modulating G protein coupled signaling. The specific aims of this proposal are (i) characterize the role of RGS10 in modulating cellular responses through the regulation of G protein activity and (ii) to investigate possible mechanisms by which RGS10 itself is regulated (via phosphorylation) in the cell. Therefore, this research plans to analyze systematically the cellular control of RGS protein function using techniques of recombinant DNA technology, biochemistry and electrophysiology.